Process for production of fuels and chemicals from biomass feedstocks

ABSTRACT

A process for the production of fuels and chemicals from biomass feedstock is provided. The process includes (a) drying the biomass feedstock using heated dry carbon monoxide gas; (b) devolatilizing the feedstock by reductive torrefaction with heated dry carbon monoxide gas; (c) pulverizing the feedstock; and (d) pyrolyzing the feedstock by reductive pyrolysis with high pressure or high temperature carbon monoxide gas. An integrated system for producing fuels and chemicals from biomass feedstock is also provided.

The present application claims priority to U.S. Patent Application No.61/608,734, filed Mar. 9, 2012, entitled Process for Production of Fuelsand Chemicals From Biomass Feedstocks, the disclosures of which arehereby incorporated by reference in their entirety.

TECHNICAL HELD

The present invention relates generally to the production of fuels andchemicals from biomass feedstocks, and more particularly tothermochemical processing of biomass feedstocks to produce fuels andchemicals.

BACKGROUND

A feedstock is defined as any renewable, biological material that can beused directly as a fuel, or converted to another form of fuel or energyproduct. Biomass feedstocks are the plant and algal materials used toderive fuels like ethanol, butanol, biodiesel, and other hydrocarbonfuels. Examples of biomass feedstocks include crop residues such as cornstover and sugarcane bagasse, energy grass crops, forestry residues,short-rotation forest crops, by-product glycerol from biodieselproduction, municipal solid waste, manures, pulp and paper residues, andspoils from demolition and disaster recovery operations.

The increasing costs associated with oil, coal and natural gas has madeusing biomass feedstocks to produce energy a promising alternative, AVan Krevelen diagram is shown in FIG. 1 and compares the hydrogen indexversus the oxygen index for various products including wood, lignin andcellulose. The diagram cross plots the hydrogen:carbon as a function ofthe oxygen:carbon atomic ratio of carbon compounds. The region on thisdiagram shows the general path from the high oxygen biomass feedstocksto lower oxygen fuels produced in nature and by prior art. The presentinvention breaks away from this region of the van Krevelen diagram byreducing oxygen with lower losses of carbon and hydrogen fuel values.

Supertorrefied wood and other biomass feedstocks produced by reductivetorrefaction by the present invention are expected to find exemplary usein achieving mandated renewable fuel co-burning in coal-fired powergeneration.

There are two primary platforms that are currently under investigationfor the production of fuels and chemicals from biomass feedstocks:thermochemical and biochemical. While neither one of these platforms hasprogressed to demonstrate commercial viability, the present invention isprimarily focused on using the thermochemical platform.

It should be noted that a significant contribution to the slow progressof the biochemical platform is the lack of an effective pretreatmentstep that delivers treated feedstock suitable for enzymatic and cellularbiochemical steps to process. The present invention, however, offerseffective thermochemical pretreatment options to accelerate progress inthis platform as well.

The primary process categories under investigation within thethermochemical platform are gasification, pyrolysis, and directliquefaction. One classification of gasification methods is based on theagent employed to treat the feedstock. The most elementary gasifier isthe air-blown type, with downdraft, updraft, sidedraft, stratified,bubbling- and circulating-fluid bed, entrained-flow, etc., typesinvestigated. Oxygen-blown and steam-blown are the next most commonlydiscussed types. Air-blown gasifiers suffer from low fuel value of gasproduced, low quality of gas produced, including contamination withwater, ash, feedstock fines, tars, and CO2. Effective gas-cleaningtechnology has yet to emerge to resolve these issues, despite extensiveresearch into water scrubbing, oil scrubbing, thermal cracking,catalytic cracking, dry filtration, and wet electrostatic filtrationmethods.

Oxygen- and steam blown systems offer higher fuel value, but havesimilar gas quality issues, and additionally require significantinvestment in auxiliary systems to provide the agent employed. Moreexotic dual and plasma gasification approaches have not yet demonstratedeconomic operation of their more capital-intensive systems.

None of these approaches to gasification rates as “good” in more thanone or two of these criteria: feedstock tolerance, syngas quality,development status, scale-up potential, and costs.

Pyrolysis systems are broadly classified into carbonization,conventional, fast, flash, ultra, vacuum, hydro-, and methano-pyrolysis.Like gasification, pyrolysis converts a feedstock containing gas,liquid, and solid matter to products consisting of gas, liquid, andsolid matter. In the most promising of these, fast pyrolysis, liquidsare the primary products. However, as produced, these liquids do notfind a ready market as fuels or chemicals. Oxygen content, viscosity,and storage stability are among the weaknesses of bio-oils produced byfast pyrolysis in finding a ready market. One limitation in pyrolysisprocesses in the current art is that liquids produced rely on gasesproduced to move them out of the reactive zone before being converted tochar.

Supercritical fluid processes employing methane, carbon dioxide, andwater as SCF medium are well known to those skilled in the art. However,these processes have not found commercial use in biomass processing.Furthermore, gas expanded liquids for processing are a more recentdevelopment and their use in biomass is not currently known. Despite itsoccurrence as a product of all thermochemical processes for biomassfeedstocks, the use of carbon monoxide as a treatment agent does notappear to have been suggested in the extensive prior art, other than itsuse as a component in synthesis gas or fuel gas.

The use of carbon monoxide as a reducing agent for solid reagents usedfor chemical looping has been described in the art. Despite itsadvantages over hydrogen for removal of oxygen from oxygenated biomassand its thermochemical derivatives, its utility does not appear to havebeen recognized.

The use of added gas in pyrolysis to provide additional carrier capacityfor liquids produced beyond that of the gases produced increases liquidyield, particularly during initial and final stages of pyrolysis whereevolved gas flowrate is low. As is recognized by those skilled in theart, gasification occurs at an equivalence ratio of approximately 0.25,and pyrolysis for positive equivalence ratios below this. The presentinvention represents thermochemical treatment at negative equivalenceratios. This produces movement along a direction on the van Krevelendiagram toward the desirable regions of lower oxygen content, withoutsacrificing either carbon or hydrogen content. The result of this isdeoxygenation of biomass feedstocks to higher caloric value fuels.

The presently disclosed process which uses carbon monoxide gas orliquid, or liquid expanded with carbon monoxide to process biomassfeedstock for fuel production is directed to overcoming one or moreshortcomings in the currently available methods.

SUMMARY

In accordance with some embodiments of the present invention, a processfor producing fuels and chemicals from biomass feedstock is provided.The process includes (a) drying the biomass feedstock using heated drycarbon monoxide gas; (b) devolatilizing the feedstock by reductivetorrefaction with heated dry carbon monoxide gas; (c) pulverizing thefeedstock; and (d) pyrolyzing the feedstock by reductive pyrolysis withhigh pressure or high temperature carbon monoxide gas.

In another aspect of the present invention, an integrated system forproducing fuel and chemicals from a biomass feedstock is provided. Thesystem includes a fixed bed; a source of heated dry carbon monoxide gasfor drying the feedstock; a source of heated dry carbon monoxide gas fordevolatilizing the feedstock; a means for pulverizing the feedstock anda source of high pressure or high temperature carbon monoxide gas forpyrolyzing the feedstock by reductive pyrolysis.

In another aspect of the present invention, a means for producing fueland chemicals is provided. The means includes (a) drying the biomassfeedstock using heated dry carbon monoxide gas; (b) devolatilizing thefeedstock by reductive torrefaction with heated dry carbon monoxide gas;(c) pulverizing the feedstock; and (d) pyrolyzing the feedstock byreductive pyrolysis with high pressure or high temperature carbonmonoxide gas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents a Van Krevelen diagram and compares the hydrogen indexversus the oxygen index for various biomass feedstock products includingwood, lignin and cellulose.

There has thus been outlined, rather broadly, certain embodiments of theinvention in order that the detailed description thereof herein may bebetter understood, and in order that the present contribution to the artmay be better appreciated. There are, of course, additional embodimentsof the invention that will be described below and which will form thesubject matter of the claims appended hereto.

In this respect, before explaining at least one embodiment of theinvention in detail, it is to be understood that the invention is notlimited in its application to the details of construction and to thearrangements of the components set forth in the following description orillustrated in the drawings. The invention is capable of aspects inaddition to those described and of being practiced and carried out invarious ways. Also, it is to be understood that the phraseology andterminology employed herein, as well as the abstract, are for thepurpose of description and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conceptionupon which this disclosure is based may readily be utilized as a basisfor the designing of other structures, methods and systems for carryingout the several purposes of the invention. It is important, therefore,that the claims be regarded as including such equivalent constructionsinsofar as they do not depart from the spirit and scope of theinvention.

DETAILED DESCRIPTION

The present invention relates to a method for processing biomassfeedstock for fuel production. In some embodiments, the biomassfeedstock is dried using a portion of carbon monoxide gas, supercritical carbon monoxide or liquid expanded with carbon monoxide. Itshould be understood that all references to carbon monoxide herein mayrefer to carbon monoxide being either solo or in mixtures with e.g.,fuel gases, hydrogen, water, carbon dioxide etc., as might be present ingas from gasification or reforming natural gas, coal bed methane orbiogas.

It is preferable to dry the biomass feedstock during processing becausethe water content will lower the energy content of the feedstock. Driedfeedstock can be further processed, pulverized for combustion fuel use,or densified for storage or transport. Wet carbon monoxide canalternatively be dried and recycled to continue to dry feedstock, storedto dry feedstock at a later time, or shifted to produce hydrogen in awater gas shift reactor.

In another embodiment of the invention, carbon monoxide gas,supercritical carbon monoxide, or liquid expanded with carbon monoxideis used to reductively devolatilize dried biomass feedstock.Devolatilized feedstock, similar to torrefied feedstock, can be furtherprocessed, pulverized for combustion fuel use, or densified for storageor transport. Carbon dioxide produced by removal of oxygen fromfeedstock and its oxygenated decomposition products can be separated andused to convert carbon in feedstock char residues to generate carbonmonoxide for use in drying or devolatilization of feedstock.

In yet another embodiment of the invention, carbon monoxide gas,supercritical carbon monoxide, or liquid expanded with carbon monoxideis used to reductively gasify devolatilized biomass feedstock. Gas andliquids produced in reducing environment offered by carbon monoxide arelow in oxygen content and thereby compatible with conventional gas andliquid fuels, as is known in the art for hydrogen treatment to upgradepyrolysis oils. Feedstock gasification residues, char of desiredcharacteristics, can be further processed, pulverized for combustionfuel use, or densified for storage or transport. Carbon dioxide producedby removal of oxygen from feedstock and its oxygenated decompositionproducts can be separated and used to convert carbon in feedstock charresidues to generate carbon monoxide for use in drying,devolatilization, or gasification of feedstock.

In yet another embodiment of the invention, carbon monoxide gas,supercritical carbon monoxide, or liquid expanded with carbon monoxideis used to reductively pyrolyze devolatilized biomass feedstock. Gas andliquids produced in reducing environment offered by carbon monoxide arelow in oxygen content and thereby compatible with conventional gas andliquid fuels, as is known in the art for hydrogen treatment to upgradepyrolysis oils. Feedstock gasification residues, char of desiredcharacteristics, can be further processed, pulverized for combustionfuel use, or densified for storage or transport. Carbon dioxide producedby removal of oxygen from feedstock and its oxygenated decompositionproducts can be separated and used to convert carbon in feedstock charresidues to generate carbon monoxide for use in drying,devolatilization, gasification, or pyrolysis of feedstock.

In yet another embodiment of the invention, carbon monoxide gas,supercritical carbon monoxide, or liquid expanded with carbon monoxideis used to reductively liquefy devolatilized biomass feedstock. Gas andliquids produced in reducing environment offered by carbon monoxide arelow in oxygen content and thereby compatible with conventional gas andliquid fuels, as is known in the art for hydrogen treatment to upgradepyrolysis oils. Feedstock gasification residues, char of desiredcharacteristics, can be further processed, pulverized for combustionfuel use, or densified for storage or transport carbon dioxide producedby removal of oxygen from feedstock and its oxygenated decompositionproducts can be separated and used to convert carbon in feedstock charresidues to generate carbon monoxide for use in drying,devolatilization, gasification, pyrolysis, or liquefaction of feedstock.

In yet another embodiment of the invention, near critical carbonmonoxide gas, supercritical carbon monoxide, or liquid expanded withcarbon monoxide is used to extract or extractively convert feedstockpolymers, oligomeric decomposition products, and monomeric products ofdepolymerization of feedstock polymers. Transport of cellulosicdecomposition products such as levoglucosan from reactive char matrixallows production of sugars in high yield.

The processes recited in the above embodiments are accomplishedthermally, without the use of a catalyst. Alternatively, the process maybe accomplished catalytically, with the use of a catalyst of homogeneousor heterogeneous type.

In some embodiments of the present invention, the process is carried outin fixed bed mode with a batch of feedstock solids. For example, thefollowing batch process may be performed:

Step Action 1 Open reactor top. 2 Charge bale. 3 Close reactor. 4 Purgereactor with exhaust gas. 5 Purge reactor with fuel gas. Divert to dumpburner on gas heater on defined criteria. 6 Flow hot gas through reactorto hot gas handling system. Divert from wet fuel gas dump burner on gasheater on defined criteria. 7 Purge reactor with exhaust gas. Divertfrom dump burner on gas heater on defined criteria. 8 Purge reactor withair. 9 Open reactor bottom. 10 Discharge reactor contents to productextruder. 11 Close reactor bottom.

In yet another embodiment according to the present invention, theprocess steps may be carried out using a cascade reactor in a continuousflow process as described in U.S. Pat. No. 3,801,469, the disclosure ofwhich is fully incorporated herein. In other embodiments, the processmay be carried out, in part using an aggressive convective dryer. In yetother embodiments of the present invention, the process may be carriedout in a containment vessel having for example, superquadratic geometryas described in U.S. patent application Ser. No. 13/774,600 entitled“Containment Vessel and Scale-Up Method for Chemical Processes,” thedisclosures of which are hereby incorporated by reference in theirentirety.

In some embodiments according to the present invention, there is anintegrated system in which biomass feedstock is dried with hot, drycarbon monoxide gas, then devolatilized by reductive torrefaction withhot, dry carbon monoxide gas, then pulverized, then converted tomethane, naptha- and diesel-range liquid fuels, and char by reductivepyrolysis with high pressure or high temperature carbon monoxide gas.Any char that is produced is used as adsorbent in purification ofliquids and gases produced by reductive pyrolysis reaction, thenoxidatively converted to ash and carbon monoxide by treatment with hightemperature or high pressure carbon dioxide in a chemical loopingconversion reaction accomplished without the addition of foreignoxygen-carrying agents.

Carbon monoxide generated beyond that needed for feedstock drying,torrefaction, and conversion is used to generate heat and electricityfor process use or external sale. Wet carbon monoxide produced in dryingand devolatilization/torrefaction is shifted to carbon dioxide andhydrogen, for process use or external sale. Gases and liquids producedin reductive pyrolysis are separated and purified for sale ashydrocarbon-compatible fuels, pipeline quality gas, and low calorificvalue fuel gas to generate heat and electricity for process use orexternal sale. Low calorific value gas streams produced in startup,shutdown, purging, and similar auxiliary operations is combusted tocontrol emissions and recover heat. Ash produced in char oxidation isfortified with missing elements and pelletized for sale as fertilizer.

The advantages of the present invention include, without limitation,simple, flexible, direct conversion of biomass feedstocks to desirablehydrocarbon fuel analogues, including pipeline quality natural gas, deansyngas, gasoline, diesel fuel, aviation fuel, milspec fuels, fuel oils,lubricants, etc., using materials native to the process astransformation agent. Further advantages include reduced yields ofundesired co-products; reduced processing temperatures, allowingconstruction from less costly alloys, especially for high halidecontaining feedstocks; reduced production of polycyclic aromatichydrocarbons, dioxins, other refractory organic compounds, and highviscosity by-products.

Additional features, advantages, and aspects of the disclosure may beset forth or apparent from consideration of the following detaileddescription, drawings, and claims. Moreover, it is to be understood thatboth the foregoing summary of the disclosure and the following detaileddescription are exemplary and intended to provide further explanationwithout limiting the scope of the disclosure as claimed.

What is claimed is:
 1. A process for producing fuels and chemicals frombiomass feedstock comprising the steps of: (a) drying the biomassfeedstock using heated dry carbon monoxide gas; (b) devolatilizing thefeedstock by reductive torrefaction with heated dry carbon monoxide gas;(c) pulverizing the feedstock; and (d) pyrolyzing the feedstock byreductive pyrolysis with high pressure or high temperature carbonmonoxide gas.
 2. The process of claim 1 wherein the carbon monoxide gasused in the drying step is super critical carbon monoxide gas or liquidexpanded with carbon monoxide gas.
 3. The process of claim 1 wherein thewet carbon monoxide gas produced from the drying step is dried and usedagain in the drying step.
 4. The process of claim 1 further comprisingthe step of reducing and gasifying the devolatized biomass feedstockusing carbon monoxide gas wherein the reducing and gasifying step occursafter the devolatilizing step and before the pulverizing step.
 5. Theprocess of claim 1 further comprising the step of reductively pyrolyzingthe feedstock using carbon monoxide gas.
 6. The process of claim 1further comprising the step of reductively liquefying devolatizedbiomass feedstock using carbon monoxide gas.
 7. The process of claim 1wherein a heterogeneous or homogeneous catalyst is used.
 8. The processof claim 1 wherein a fixed bed reactor is used to carry out the processsteps in a batch process.
 9. The process of claim 1 wherein the processis carried out in a continuous flow process.
 10. The process of claim 1wherein the feedstock is converted to one of the group consisting of:methane, naptha and diesel range liquid fuels.
 11. An integrated systemfor producing fuel or chemicals from biomass feedstock comprising: afixed bed reactor; a source of heated dry carbon monoxide gas for dryingthe feedstock; a source of heated dry carbon monoxide gas fordevolatilizing the feedstock; a means for pulverizing the feedstock; asource of high pressure or high temperature carbon monoxide gas forpyrolyzing the feedstock by reductive pyrolysis.
 12. The system of claim11 wherein the carbon monoxide gas used to dry the feedstock is supercritical carbon monoxide gas or liquid expanded with carbon monoxidegas.
 13. The system of claim 11 wherein wet carbon monoxide gas producedfrom drying the feedstock is dried and used again to dry the feedstock.14. The system of claim 11 further comprising the step of reducing andgasifying the devolatized biomass feedstock using carbon monoxide gaswherein the reducing and gasifying step occurs after the devolatilizingstep and before the pulverizing step.
 15. The system of claim 11 furtherwherein the feedstock is reductively pyrolizing the feedstock usingcarbon monoxide gas.
 16. The system of claim 10 wherein the devolatizedbiomass feedstock is reductively liquefied using carbon monoxide gas.17. The system of claim 10 wherein a heterogeneous or homogeneouscatalyst is used.
 18. The system of claim 10 wherein the feedstock isconverted to one of the group consisting of: methane, naptha and dieselrange liquid fuels.
 19. The system of claim 10 wherein the fuel andchemicals are produced in batch process.
 20. A means for producing fuelsand chemicals from biomass feedstock comprising the steps of: (a) dryingthe biomass feedstock using heated dry carbon monoxide gas; (b)devolatilizing the feedstock by reductive torrefaction with heated drycarbon monoxide gas; (c) pulverizing the feedstock; and (d) pyrolyzingthe feedstock by reductive pyrrolsis with high pressure or hightemperature carbon monoxide gas.